Wednesday, July 20, 2011

Forecast Discussion- Minnesota/Wisconsin (July 20)( 11 AM CDT)

EHI: Spinning and energy in the atmosphere. Values above 2 considered elevated.

STP: Values above 1 considered elevated

SCP: Values above 4 considered elevated
SCP: Supercell Composite. Shows chance for supercells.
EHI: Energy Helicity Index. See image w/ caption for description
STP: Significant tornado parameter. Values above 2 associated with F2+ tornadoes.

Discussion... Cold front in question to ignite thunderstorms in WI/MN is currently beginning its trek eastward from the Dakotas.
It looks like thunderstorms have already developed ahead of the cold front in the Dakotas, as several outflow boundaries have surfaced near the cold front itself.
Convection should begin this afternoon for MN/WI

Big issue is model runs. Have just observed 14z run of RR, which indicates no convection should occur in MN. Showers and an isolated storm instead. Observing the 13z HRRR ignited an MCS (storm cluster) in MN and tracked sharply NE, missing Wisconsin. HRRR indicates MCS in MN may become tornadic, as close detail indicates a more hook-like cell in the MCS.
14z RUC appears to attempt and initiate convection in East Central Minnesota, but appears to die out. A small bowing structure forms at about 5 pm in far NE Minnesota and that evolves into a smaller MCS as it moves into Canada.

In summary...whole idea of severe storms this afternoon is clouded by the models. Indicators posted above in images appear to favor Wisconsin, so this may be a case of wrong place, right time for WI/MN.
Will post later updates as this confusion will warrant another look.

No comments: